It is known for cards and cleaning machines to be supplied by means of pneumatic conveying lines with fiber flocks which are separated from the conveying air by a separator and supplied to a feed chute which is usually positioned below the separator.
A chute of this kind has been described, for example, in an article entitled "Die Neue Kardenspeisung Aerofeed-U", published in the February 1986 issue of the journal "mittex". The article discloses that the pneumatically supplied flocks are conveyed by means of a separating head into a feed chute in which the flocks are separated from the air conveying them.
The flocks are delivered from the chute by means of feed rollers and supplied by way of an opening cylinder to a second stock chute lower down, from which they are delivered by means of a pair of non-displaceable delivery rollers and, through the agency of one of the two such rollers and of another displaceable pressing roller, are conveyed further, for example, to a guide plate of a card.
The pressing roller is either weight-biased or spring-biased so that resulting pressure consolidates or compresses the web at a predetermined pressure.
A disadvantage can arise in connection with the use of such arrangements. When the card is stopped and delivery of the feed web ceases for a time, even though temporarily, a compressed zone is produced in the web because of the pressing between the pressing roller and the delivery roller. This zone does not return to its original shape after regular machine operations are resumed. That is, a web zone that has been compressed for a time between stationary rollers will not spring back to anything like the same extent as a web which has been fed continuously through such a compression zone. The web could be said to "breathe" much less in a zone compressed for a time between stationary feed means than in the rest of the web which has been compressed at the same pressure but while being conveyed continuously.
Such indentations or more highly compacted zones in the fiber web being supplied to the carding instrumentalities have been found to be sources of irregularities in slivers produced by the card. Such irregularities are undesirable, particularly in systems which include automatic control systems intended to make possible the production of uniform slivers.